Anchor-Free Range-Free 3D IoT Localization in Buried Environments with Connectivity-Informed Power Selection and Temporal Refinement

In underground and surface mines, wireless Internet-of- Things (IoT) tags deployed with ore or muck loads can support material and grade tracking after burial, when conventional ranging and surveyed localization infrastructure may be unavailable. Building on the three-dimensional Pro- traction Technique (3D-PT), this paper introduces 3D-PT with Power Selection (3D-PT-PS), which selects informative transmit-power levels from binary pilot measurements, and 3D-PT-PS with Temporal Refinement (3D-PT-PST), which incorporates recorded load-deposition times as weak, non- metric cues. Both methods are anchor-free and range-free and require no RSSI, measured ranges, surveyed anchors, pile dimensions, or material parameters. Monte Carlo simulations evaluate different pile sizes and tag densities. In a 5000-t crusher-pocket scenario with 125 tags, 3D-PT-PST achieves 6.12% mean NRMSE and 2.20 m 3D RMSE, reducing mean NRMSE by 13.5% relative to 3D-PT-PS and by 43.6% and 69.1% relative to calibrated MDS-MAP(P) and CATL, respectively. These results show that connectivity and timing provide complementary information.